An Economics Evaluation of Rainwater Harvesting For Green Space: A Case Study of Mashhad, Iran

Nowadays, one of the main goals of the city council is to extend the green environment and health for their citizens to improve their quality of life. Water is the main limiting factor for this purpose in Mashhad. The economic evaluation of the project is considered one of the most important sections as the funding source is limited and it is not important who pays the cost and who will benefit in a public project. This issue has to be taken into consideration via economic values for all multi factors and multi goals in social activities. As the cost was paid at the first part and income will be earned later, it is necessary to determine a communal temporal basis for expenses and income. Therefore, the expenses and incomes have to be changed for the same date. For this purpose, the future income was adjusted to current date that it is called befit to cost ratio. The results showed that the benefit to cost ratio is 1.14 for rain harvesting in this project and they also indicated that the project's economic annual rate is 5 %. In other words, after 30 years it will be able to cover its cost.